Following T. Z. Tang and R. J. DeRubeis's (1999) report of sudden gains (a sudden and substantial improvement in depression symptoms in one between-session interval) in cognitive-behavioral therapy (CBT) for depression, this study explored sudden gains in supportive-expressive (SE) psychotherapy. Studies suggested that CBT sudden gains are caused by cognitive changes, which is a factor specific to CBT. Thus, sudden gains might not be expected in SE psychotherapy. Contrary to that expectation, sudden gains in SE psychotherapy were found, and they showed similar magnitude, affected a similar percentage of patients, and occurred at about the same time in treatment as CBT sudden gains. However, the symptom gains from the SE psychotherapy sudden gains were much less stable than the CBT sudden gains and showed a much higher rate of reversal before treatment ended. The long-term benefits of SE psychotherapy sudden gains also appear less robust than CBT sudden gains.